Imaging and visualization techniques for assisting ophthalmic surgeons are becoming increasingly popular, and much research and development is being conducted regarding these techniques. One class of ophthalmic surgeries, the vitreo-retinal procedure, involves vitrectomy, the removal of the vitreous body from the posterior chamber to access the retina. The successful execution of vitrectomy requires an essentially complete removal of the vitreous, including the most challenging regions near the vitreous base. Using imaging techniques and devices can be of substantial help to improve the efficiency of the vitreous removal.
However, assisting vitrectomy with imaging is particularly challenging for several reasons. One of them is that the vitreous is transparent. Another challenge is that visualization of the periphery requires imaging beams with a high angle of obliqueness. Similar visualization issues exist during membrane peeling procedures. At present, typically microscope or video-microscope imaging is used to address the former challenge, and wide angle contact-based or non-contact based lenses are used to address the latter challenge, in each case with limited success.
Improvement of the imaging can be achieved by using optical coherence tomography (OCT), a technique that enables visualization of the target tissue in depth by focusing a laser beam onto the target, collecting the reflected beam, interfering the reflected beam with a reference beam and detecting the interference, and measuring the reflectance signature within the depth of focus of the beam. The result is a line scan in depth, a cross-sectional scan, or a volumetric scan.
Conventional diagnostic ophthalmic OCT systems use retinal tracking to track the motion of the retina. In such system, an initial fundus image may be acquired by a fundus imager and set as a reference. Sequential fundus images may be taken in real-time and compared to the reference fundus image to track the relative motion of the retina, which is then used as a feedback to the OCT scanner so that the OCT system is always tracking and scanning the same area of the retina. However, scanning a fixed and predetermined area does not necessarily provide the useful information surgeons may need as, during surgery, surgeons are often more concerned about those area directly underneath or close to the surgical instrument. Accordingly, certain embodiment of the present disclosure may beneficially provide an OCT system that that facilities increased surgeon control over the scanning location.